Art of pumping mercury



July 3, 1951 R. B. COX

ART OF PUMPING MERCURY Filed June 1, 1946 Brine Inlet Patented July 3,1951 ART OF PUMPING MERCURY Robert B. Cox, Wyandotte, Mich., assignor toWyandotte Chemicals Corporation, Wyandotte, Mich., a corporation ofMichigan Application June 1, 1946, Serial No. 673,762

6 Claims. (Cl. 103-260) The present invention relates to an improvedmethod of pumping liquid mercury, and a pumping system for same.

Considerable difiiculty has arisen in the past in producing a forcedflow, i. e. in pumping liquid mercury or an amalgam having the samephysical characteristics as the liquid mercury itself. Due to therelatively high specific gravity of the mercury, it has previously beenthought necessary to use a positive displacement type of mechanicalpump, or one whose moving parts act directly on the mercury. Mercury,however, has the tendency to amalgamate with, or dissolve, many othermetals and elements. See British Chemical Abstracts, Applied Chemistry,1927, page 304.

Therefore, in the art of pumping mercury, the severe problem ofamalgamation of the fluid mercury with the metallic parts of amechanical displacement type of pump, has always been present. Thisproblem is particularly acute in the industrial electrochemical art inthe operation of mercury cathode brine cells where it is necessary tohandle and transfer a large volume of mercury, both in the form ofsodium amalgam (sodium being soluble in mercury to the extent of about 8parts in 1000) and in its denuded form.

My present invention is therefore particularly well suited for use withsuch a mercury cathode electrolytic cell as disclosed in my co-pendingapplication Serial No. 576,041 filed February 3, 1945.

I have discovered that mercury in its liquid form can be entrained in arapidly flowing stream of relatively lighter liquid which is inert andsubstantially non-reactive with respect to mercury. Such lighter liquidmay be water or an aqueous solution containing other dissolved chemicalcompounds, such as a caustic soda solution, or it may be an organicliquid such as a liquid hydrocarbon having a specific gravity andviscosity equivalent to that of water. The mercury is therebytransported or pumped along with the lighter vehicular stream to adesired point of delivery. Due to the relatively great differences inthe specific gravities of mercury and the vehicular liquid, they canthen be readily separated from each other, prior to contact of themercury with the parts of a mechanical pump, so that it is possible touse an ordinary water. pump in my mercury pumping system,

My invention possesses the additional advantage, in that the conduits inwhich the mercury or sodium amalgam is flowed, can be made from amaterial such as glass, .or a synthetic resin so that there is no dangerof the mercury or sodium amalgam dissolving or reacting with the conduitelements with which it does come in contact.

My invention is of particular advantage when used in conjunction with asodium-amalgam electrolytic process, as it renders possible an unusualreduction in the amount of mercury required for operation of theprocess, since the volume of mercury that would otherwise be necessaryto fill pumps, conduits, reservoirs, etc., is greatly reduced andbecause such volume is primarily occupied by the vehicular liquid. Ithas been found that my invention renders it possible to reduce to aboutone-half the mercury volume requirement (representing a large proportionof the material cost) of a moving mercury cathode cell, such asdisclosed in my aforesaid co-pending application.

I have also made the discovery that the rate of flow of the water streamwith which the mercury is entrained, must be at or above a certainspecified critical velocity, in order to effect satisfactory operation.

Additional objects and advantages of my invention shall become apparentas the following description proceeds.

To the accomplishment of the foregoing and related ends and to enableany person skilled in the art readily to understand and practice theinvention, the following full and concise description and annexeddrawing set forth the best mode in which I have contemplated applyingthe principle of my invention.

In said annexed drawing Fig. 1 is more or less a diagrammatic viewillustrating the mercury pump system embodying the principle of myinvention and;

Fig. 2 is a top plan View of the chamber for separating the entrainedmercury from the vehicular water stream.

Now referring more particularly to the drawing, there are shown thereina conduit I leading from a source of mercury supply and connected at thepoint 2 to the conduit 3, the latter being part of the vehicular waterstream or loop. A

stream of water is introduced to the conduit 3 3 from the conduits 4 and5 leading from the water pump P. The velocity of the water stream in theconduits 3, 4 and 5 is much greater than that of the mercury in theconduit I. As substantially illustrated in Fig. 1, the mercury, onentering the water stream, is broken up and en-' trained in the form ofelongated globules 6 and thus lifted or pumped to a higher elevation.

In Fig. 1, the source of mercury entering the conduit l is shown asderived from the sodium amalgam outlet 1 in the bottom of the vertical,electrolytic brine decomposition cell 8, such as shown and described ingreater detail in my aforesaid co-pe'nding application. Fresh mercury,

derived from the stripping or denuding cell where the sodium amalgam isreacted to form caustic soda, hydrogen and mercury, is introducedthrough the inlet 9 and the electrode nozzles ID to the top of the cell8. I

A flared or diverging connection 'll leads from the conduit 3 to theinlet 12 on the outer periphery of the separating chamber 13. The latterchamber I3 is preferably of a circular shape. .Its bottom is dishedinwardly to form a central raised portion, as indicated at M, and thusforming a ring-like space around the outside portion of the bottom ofthe chamber l3 where the mercury or sodium amalgam is collected asindicated at [5 whence it is drained out through the outlet I6 connectedthrough a suitable U-tube trap to the outlet conduit ll. From theconduit 11, the sodium amalgam may suitably be lead to a stripping ordenuding cell.

The heavier mercury is thus separated from the Water stream in thechamber l3. Due to the fact that the velocity of the Water stream issubstaneffect of the vehicular stream velocity to entrain such mass.

The mercury-free water rises up through .the

central neck or constricted portion I4 of the chamber [3 whence itpasses through the connecting conduit l9 back to the pump P.

The conduit with a suitable valve connected therein, leads from a watersupply source (not shown) to the conduit IQ for the purpose ofreplenishing the amount of water which might be required from time totime in the water circuit or loop. A gas conduit 2| is connected in theupper end of the separating chamber neck l3 for leading off any smallamount of gas that might be generated.

' I have discovered that the linear velocity of the lighter fluid, suchas the water in the conduit 3,

must be at or above a critical minimum of 19 inches per second. Apracticable velocity, to accommodate line surges and maintain uniform:operation, is about 50% greater than this critical minimum, or 28.8inches per second. Of course, a slight pressure or head must bemaintained on the mercury in the conduit I, which is at least equal tothe pressure of the vehicular water stream in the conduit 3. A mercurypressure or head of about 5 inches in the conduit I will renderitpossible to lift or pump the liquidmer- 4 cury to a height of severalfeet in the conduit 3. It will be apparent to those skilled in the art,that my above described invention may be equally well used for pumpingfiuid mercury or fluid amalgams in environments other than in connectionwith a sodium-amalgam electrolytic cell,

and that other vehicular liquids may be employed beside the waterreferred to in the foregoing detailed description. Thus, a weak causticsoda solution will operate equally as Well as Water in the systemdescribed.

In the appended claims, the term liquid mercury is intended to includein its scope liquid mercury containing dissolved or amalgamated metalsor elements, as long as the resultant body maintains essentially thephysical characteristics of liquid mercury itself.

Equivalent modes of practicing my invention may be followed providedthat they are within the scope and purview of the appended claims.

I, therefore, distinctly claim and particularly point out as myinvention:

1. The method of pumping mercury which comprisesintroducing liquidmercury into an aqueous stream moving at a linear velocity greater than19 inches per second, the head of said mercury being at least equal tothat of said aqueous stream at the point of entrainment.

2. The method of pumping mercury which comprises entraining a body ofliquid mercury in a rapidly flowing aqueous stream said stream being ofsubstantially constant pressure and velocity throughout its vehicularlength, introducing said mercury into said stream at a head at leastequal to that of said stream, separating the mercury from such stream bydecreasing the velocity thereof, increasing the velocity of said streamand recycling it to the pumping system.

3. The method of pumping mercury which comprises inducting the liquidmercury into a conduit containing a rapidly flowing aqueous stream saidstream being of substantially constant pressure and velocity throughoutits vehicular length, introducing said mercury into said stream at ahead at least equal to that of said stream, introducing such stream intothe bottom .of :an enlarged chamber, therein separating out a themercury therefrom and returning the mercury-free stream to the pumpingsystem.

4. The method of pumping mercury which comprises inducting the liquidmercury into a conduit containing an aqueous stream flowing at a linearvelocity of greater than 19 inches per second, the head of said mercurybeing at least equal to that of said aqueous stream at the point ofentrainment, introducing the mercury-entrained stream into the bottom ofa circular chamber having a larger cross-sectional area than that ofsaid conduit, withdrawing the mercum from the'bottom of said chamber,and withdrawing the mercury-free stream from the top of said chamber.

.5.'The method of pumping mercury which comprises introducing a bod ofliquid mercury, at a given point of elevation, into an upwardly flowingvehicular stream of relatively lighter liquid, said stream being ofsubstantially constant velocity throughout its vehicular length, thehead of said mercury body at such point of introduction being at leastequal to that of said stream, entraining said mercury body in saidvehicular stream, and lifting the so-entrained mercury to a second pointof elevation higher than that attainable by the head of said mercurybody itself.

6. The method as in claim 5 including the additional steps ofintroducing the mercuryentrained stream at said second point ofelevation into the bottom of an enlarged chamber, imparting a rotarymotion to the path of flow of said stream in said chamber, andmaintaining said stream at such a linear velocity that the resultantcentrifugal and gravitational forces exerted thereon operate to separatethe mercury therefrom.

ROBERT B. COX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 619,349 Reicken Feb. 14, 1899734,499 Baker et a1 July 28, 1903 Number Number OTHER REFERENCES BritishChemical Abstracts, Applied Chemistry, 1927, page 304.

